Print member guide and return means for selective printing machines



PRINT MEMBER GUIDE AND RETURN MEANS FOR SELECTIVE PRINTING MACHINES Filed Jan. 13, 1965 2 Sheets-Sheet 1 April 25, 1967 ELSNER PRINT MEMBER DE AND RETURN MEANS FOR SELECTIVE PRINTING MACHINES 7 Filed Jan. 13, 1965 2 Sheets-Sheet 2 la n a IN VEN TOR Iva-17b EKJWEJ' United States Patent 9, 4 Claims. (Cl.101--109) The present invention relates to a printing hammer arrangement, and more particularly to printing apparatus in which type carriers in the form of endless bands move past the end faces of a row of printing hammers which are movable transverse to the printing surface and are advanced by electromagnetic means to press selected types against the printing surface.

Since printed characters are usually spaced along a line at distances of approximately 2.4 to 2.8 mm., the corresponding thickness of the printing hammers must be less than this distance.

Printing apparatus according to the prior art serving this purpose provides prismatic printing hammers which are guided in a comb-shaped supporting body. Springs are provided for urging the printing hammers to a retracted position, and these springs are coil springs having an outer diameter greater than the thickness of the printing hammers and than the corresponding guide grooves in the supporting body.

The printing hammers according to the prior art have printing heads at the ends cooperating with the type carriers which serve as abutment during the return movement of the printing hammers and engage a corresponding stop face on the guide body. Since the return springs laterally project from the printing hammers, they engage the inner guide surfaces of the walls of the guide grooves.

The apparatus according to the prior art has disadvantages which are particularly apparent at high printing speeds, and the manufacture of the printing hammers is comparatively diflicult and expensive.

For example, if a spacing of 2.6 mm. corresponding to the width of the type characters and a thickness and diameter of the return springs of 2.1 mm. are assumed, the thickness of the printing hammers is only 1.5 mm., if the springs project on either side of the respective printing hammer a distance of 0.3 mm.

Since one end of the printing hammer is hit by a movable member of an electromagnetic means and the other end engages the hardened type carrier, the printing hammers must be hardened in order to avoid wear on the guided parts thereof. It is well known that metal parts of small thickness are easily distorted by a hardening operation, and since the printing hammers may become hot during high speed printing operations, a corresponding distortion may occur, and cause jamming of the printing hammers in the guide grooves.

Due to the fact that the printing hammers of the prior art have transversely projecting hammer heads, it is not possible to grind the printing hammer in a single operation along the lateral faces thereof, which is indispensable if a smooth sliding fit, and low noise operation is to be obtained.

The arrangement of the return springs according to the prior art has the disadvantage that the springs buckle upon the impact of the printing hammers, and urge the same against the top face of the respective guideway. Due to the developed high friction, the return stroke of the printing hammers is detrimentally aflected.

Furthermore, when the printing hammers are stopped after the return stroke by engagement with a metal stop member, the printing hammers tend to bounce back, which may result in smudged and duplicated imprints,

particularly for small printing strokes in high speed printing apparatus.

It is the object of the present invention to overcome the disadvantages of the prior art printing hammer arrangements, and to provide a printing hammer arrangement of compact construction which operates reliably even at high speeds, and can be inexpensively manufactured to very precise tolerances.

Another object of the invention is to prevent engagement of the return springs with the guide faces by which the printing hammers are guided.

Another object of the invention is to provide a printing hammer arrangement in which the space available due to the width of the type characters, is used for the printing hammers rather than for the return springs.

Another object of the invention is to provide printing hammers which are bounded by planar faces along the entire length thereof and have no projecting printing heads.

Another object of the invention is to provide a stop member which simultaneously serves as abutment for the return springs, and as a stop for stopping movement of the printing hammers under the action of the return springs.

The printing hammers according to the present invention are mounted for sliding movement in guide grooves which have such a transverse width that the thickness of the printing hammers can be made, for example, 2.1 mm. if the width of type character is 2.6 mm.

With the above objects in view, the present invention relates to a novel and improved printing hammer arrangement in printing apparatus of the type in which printing hammers are actuated by electromagnetic means and engage type carriers to urge the same against a printing surface. One embodiment of the invention comprises supporting means having a plurality of parallel guideways; a plurality of printing hammers movably disposed in the guideways and having pairs of spaced engaging portions; a stop member, preferably a bar of rectangular cross section, extending transverse to the guideways across the printing hammers between the engaging portions of the same; and a plurality of spring means, each of which engages the stop member and one of the engaging portions of a printing hammer.

The spring means bias the respective printing hammers for movement along the respective guideway to a position of rest in which the other engaging portion of the printing hammer abuts the stop member.

When an electromagnetic actuating means drives a printing hammer toward the type carrier and the printing surface, the respective spring means is compress ed, and the respective engaging portion moves away from the stop member.

. During such movement, the compressed spring tends. to buckle, and in accordance with the present invention, a concave recess is provide in the bottom face of the guide groove to receive and support a compressed and buckling spring, so that lateral buckling of the springs, and sliding of the same on the lateral surfaces of the guide grooves is prevented.-

Each of the printing hammers is bounded by planar faces along the entire length thereof, and has a rectangular cross section, with a cutout bounded by the engaging portions. The springs are respectively located in the cutouts through which the stop member extends in a direction transverse to the direction of the movement of the printing hammers.

In the preferred embodiment of the invention the stop member is a bar made of an elastic synthetic material. The guide grooves are provided in two parallel ridges of a supporting body and are closed by a cover abutting the supporting body. Consequently, each printing hammer guided by the lateral IStop bar 4 extends printing hammers are only partly in sliding contact with the guide grooves whereby the friction is reduced.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a cross sectional view illustrating one embodiment of the invention;

FIG; 2 is a cross sectional view illustrating a detail of FIG. 1 in another operational position; and

FIG. 3 is a fragmentary perspective view, partially in section and broken off, illustrating the embodiment of FIGS. 1 and 2.

Referring now to the drawings, a supporting body 1 has four spacing portions 1g, 1h, 1g and 1h on which a cover 5 rests. The supporting body has two ridges 1c and 1d which are of lesser height than the spacing portions. A row of parallel guideways is provided in the ridges, each guideway including aligned guide grooves 1a and 1b which are spaced from each other. In this manner, walls are formed between the guide grooves which do not extend to the bottom face of the cover 5. Each of the guide grooves 1a, 1b has a rectangular cross section. The spacing of the guideways corresponds to the space required for a printed character.

Printing hammers 2.are mounted in each pair of grooves 1a, 1b forming a guideway for the printing hammer. A rectangular cutout 2a is provided in each printing hammer and is having confronting abutment faces 2b and 20, as best seen in FIG. 2. The height of each printing hammer corresponds to the space between the bottom face 11' of the .respective guide groove and the bottom face So of the cover member 5, so that the parallel and planar top and bottom faces of the printing hammers 2 are guided. The lateral planar parallel faces of the printing hammers are faces of the walls between the guide grooves, and since the walls are of lesser height than the printing hammers, only the lower portions of the printing hammers are in sliding engagement with the lateral faces of the guide grooves 1a and 1b- Coil springs 3 are .mounted in the cutouts and have ends engaging the abutment faces 21). The other ends of springs 3 abut a stop bar 4 of rectangular cross section which is inserted into a recess 1e in supporting body 1.

in a direction transverse to the direction of the guideways 1a, 1b and closes the inner ends of guide grooves in by abutting the end faces of the separating walls. The height of the portion of stop bar 4 which projects above the recess 1e, corresponds to the height bounded by two engaging portions of the walls between the grooves, and to the height of the ridges 1c and 1d.

The upper portion of stop bar 4 projects into the cutouts 2a of the printing hammers 2, and supports the other ends of springs 3 so that the springs urge the printing hammers to the left as viewed in FIG. 1 until the abutment face 2c abuts the side of the stop bar remote from the side engaged by springs'3. However, when the movable member 6 of an electromagnetic actuating means shown on the left side of FIG. 1 is actuated and turned in counterclockwise direction, the respective printing hammer is engaged and moved to the right'as viewed in FIGS. 1 and 2 to the printing position shown in FIG. 1 in which the abutment face 2c is spaced from stop bar 4, and the right hand end of the respective actuated printing hammer engages a carrier of a printing type, not shown, to produce an imprint.

When the electromagnetic means is de-energized,

project from the the lateral faces of the guide grooves 1a in which the cut spring 3 returns the respective actuated printing hammer 2 to the normal position of rest shown in FIG. 1 in which the abutment face 2c abuts stop member 4.

As best seen in FIG. 3, each coil spring 3 has adiameter corresponding to the thickness of the respective printing hammer 2 so that the coil spring does not laterally printing hammer and cannot engage out 2a and the spring 3 are located. However, in the printing position shown in FIG. 2, the coil spring 3 is compressed, and consequently has a tendency to buckle. In order to provide an engagement between the coil spring and the lateral guide faces of guide grooves 1a, 1b, a concave recess is provided in the bottom face 1i of each guide groove in which permits a downward buckling of the respective spring 3 into the concave recess 1].

When the electromagnetic means hammer 2 for return movement under the action of spring 3, abutment face 20 rapidly moves toward stop member 4, and engages the same with respective printing hammer 2. In order to reduce the noise and to dampen the impact, stop member 4 is preferably made of an elastic, preferably synthetic material. Due to the damping action of stop member 4, a bouncing back of a stopped printing hammer is prevented.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of printing hammer arrange ments differing from the types described above.

While the invention has been illustrated and described as embodied in a printing hammer arrangement including acteristics of the generic or specific aspects of this invention and, therefore,,such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a printing apparatus, in combination, supporting means having a plurality of parallel guideways, each guideway having a portion withv a curved recess; a plurality of printing 7 respectively, for longitudinal movement, each printing hammer having a cutout bounded by one engaging portion and another engaging portion arranged longitudinally spaced from each other; a stop member extending transverse to said guideways across said printing hammers through said cutouts between said engaging portions of each printing hammer; means for moving any'of said printing hammers during the printing phase into a position in which said other engaging portion of said printing hammer is spaced from said stop member; and a plurality of spring means, each spring means engaging said stop:

means having a plurality of parallel guideways, each. .guideway having a portion with a curved recess, each guideway having a predetermined transverse extension; a

releases, a printing an impact to stop the is not intended to be limited to the hammers disposed in said guideways,

plurality of printing hammers having a transverse thickness corresponding to said transverse extension and being slidingly guided in said guideways, respectively, for longitudinal movement, each printing hammer having a rectangular cross section and a cutout bounded by one engaging portion and another engaging portion arranged longitudinally spaced from each other and being bounded along the entire length thereof by a pair of planar lateral faces and by planar top and bottom faces; a stop member extending transverse to said guideways across said printing hammers through said cutouts and between said engaging portions of each printing hammer; means for moving any of said printing hammers during the printing phase into a position in which said other engaging portion of said printing hammer is spaced from said stop member; and a plurality of spring means respectively located in said cutouts, each spring means having a transverse thickness substantially equal to said transverse thickness of the respective printing hammer and engaging said stop member and one of said engaging portions of said printing hammers, respectively, to bias the respective printing hammer for movement along the respective guideway to a position of rest in which the other engaging portion of the respective printing hammer abuts said stop member, each said spring means being located in said portion of the respective guideway so as to be received by said curved recess in a bent and compressed condition While said other engaging portion is spaced from said stop member.

3. In a printing apparatus, in combination, a supporting body having first and second parallel projecting ridges extending in one direction, said ridges having, respectively, a plurality of first and second parallel guide grooves, said first grooves having concave bottom faces, respectively, pairs of first and second guide grooves being aligned in a direction transverse to said direction and forming guideways; a plurality of printing hammers respectively disposed in said guideways for movement along the same, eac-h printing hammer having a cutout located in the region of the respective first guide groove and being bounded by one abutment face and another abutment face arranged spaced from each other; a stop bar secured to said supporting body extending in said one direction and being located between said first and second guide grooves and at the ends of said first guide grooves to close the same; means for moving any of said printing hammers during the printing phase into a position in which said other abutment face is spaced from said stop bar; and a plurality of springs respectively located in said cutouts and extending along the length of the respective printing hammer, each spring having one end abutting one of said abutment faces and another end abutting said stop bar to bias the respective printing hammer for movement along the respective guideway to a position of rest in which the other abutment face of the respective printing hammer abuts said stop bar, each said springs being located in one of said first guide grooves so as to abut said concave bottom face in a bent and compressed condition while said other abutment face is spaced from said stop bar.

4. In a printing apparatus, in combination, a supporting body having first and second parallel projecting ridges extending in one direction, said ridges having, respectively, first and second sets of parallel walls forming between each other a plurality of first and second parallel guide grooves, said first grooves having concave bottom faces, respectively, of rectangular cross section, pairs of first and second walls and guide grooves being aligned in a direction transverse to said direction and forming guideways, said supporting body having spacing portions higher than said walls; a cover plate resting on said spacing portions and closing said guideways spaced from said walls; a plurality of printing hammers of rectangular cross section respectively disposed in said guideways for movement along the same, each printing hammer having a cutout located in the region of the respective first guide groove and being bounded by one abutment face and another abutment face arranged spaced from each other; a stop bar of rectangular cross section secured to said supporting body extending in said one direction and being located between said first and second guide grooves and at the ends of said walls between said first guide grooves to close the same, said stop bar consisting of an elastic material; means for moving any of said printing hammers during the printing phase into a position in which said other abutment face is spaced from said stop bar; and a plurality of coil springs respectively located in said cutouts and extending along the length of the respective printing hammer, each spring having one end abutting one of said abutment faces and another end abutting said stop bar to bias the respective printing hammer for movement along the respective guideway to a position of rest in which the other abutment face of the respective printing hammer abuts said stop bar, each said springs being located in one of said first guide grooves so as to abut said concave bottom face in a bent and compressed condition While said other abutment face is spaced from said stop bar.

References Cited by the Examiner UNITED STATES PATENTS 1,780,674 11/1930 Ewald 101-109 1,853,211 4/1932 Hofimann 101-109 X 2,010,652 8/1935 Tauschek 101-109 X 2,606,491 8/1952 Wockenfuss 101-109 2,874,634 2/1959 Hense 101-93 2,935,018 5/1960 Lego 101-109 2,995,082 8/1961 Sasaki 101-109 3,144,821 8/1964 Drejza 101-93 W LL A B, PENN, Primary Examiner. 

1. IN A PRINTING APPARATUS, IN COMBINATION, SUPPORTING MEANS HAVING A PLURALITY OF PARALLEL GUIDEWAYS, EACH GUIDEWAY HAVING A PORTION WITH A CURVED RECESS; A PLURALITY OF PRINTING HAMMERS DISPOSED IN SAID GUIDEWAYS, RESPECTIVELY, FOR LONGITUDINAL MOVEMENT, EACH PRINTING HAMMER HAVING A CUTOUT BOUNDED BY ONE ENGAGING PORTION AND ANOTHER ENGAGING PORTION ARRANGED LONGITUDINALLY SPACED FROM EACH OTHER; A STOP MEMBER EXTENDING TRANSVERSE TO SAID GUIDEWAYS ACROSS SAID PRINTING HAMMERS THROUGH SAID CUTOUTS BETWEEN SAID ENGAGING PORTIONS OF EACH PRINTING HAMMER; MEANS FOR MOVING ANY OF SAID PRINTING HAMMERS DURING THE PRINTING PHASE INTO A POSITION IN WHICH SAID OTHER ENGAGING PORTION OF SAID PRINTING HAMMER IS SPACED FROM SAID STOP MEMBER; AND A PLURALITY OF SPRING MEANS, EACH SPRING MEANS ENGAGING SAID STOP MEMBER AND ONE OF SAID ENGAGING PORTIONS OF SAID PRINTING HAMMERS, RESPECTIVELY, TO BIAS THE RESPECTIVE PRINTING HAMMER FOR MOVEMENT ALONG THE RESPECTIVE GUIDEWAY TO A POSITION OF REST IN WHICH THE OTHER ENGAGING PORTION OF THE RESPECTIVE PRINTING HAMMER ABUTS SAID STOP MEMBER, EACH SAID SPRING MEANS BEING LOCATED IN SAID PORTION OF THE RESPECTIVE GUIDEWAY SO AS TO BE RECEIVED BY SAID CURVED RECESS IN A BENT AND COMPRESSED CONDITION WHILE SAID OTHER ENGAGING PORTION IS SPACED FROM SAID STOP MEMBER. 